BPA Findings Highlighted at AAAS Annual Meeting

Meta-analyses of bisphenol A studies show human exposure is likely to be too low for estrogenic effects

A controversial component of plastic bottles and canned food linings that have
helped make the world's food supply safer has recently come under attack:
bisphenol A. Widely known as BPA, it has the potential to mimic the sex hormone
estrogen if blood and tissue levels are high enough. Now, an analysis of almost
150 BPA exposure studies shows that in the general population, people's
exposure may be many times too low for BPA to effectively mimic estrogen in the
human body.

The
analysis, presented at the American Association for the Advancement of
Science's (AAAS) annual meeting February 16 in Boston, Mass., by Pacific
Northwest National Laboratory toxicologist Dr. Justin Teeguarden, shows that
BPA in the blood of the general population is many times lower than blood
levels that consistently cause toxicity in animals. The result suggests that
animal studies might not reflect the human BPA experience appropriately.

"Looking
at all the studies together reveals a remarkably consistent picture of human
exposure to BPA with implications for how the risk of human exposure is
interpreted," said Teeguarden. "At these exposure levels, exposure to
BPA can't be compared to giving a baby the massive dose of estrogens found in a
birth control pill, a comparison made by others."

Teeguarden's
talk was part of an AAAS public policy symposium he chaired titled "Can Exposure Science
Quell the Furor over Environmental Endocrine Disruption?" He and speakers from
the Harvard School of Public Health, the U.S. Food and Drug
Administration's National Center for Toxicological Research, and the University
of Edinburgh presented the latest
information about this important industrial compound, which is at the epicenter
of a heated debate.

In
addition to evaluating the likelihood of BPA mimicking estrogen in humans, Teeguarden
also analyzed another set of BPA studies that looked at the chemical's toxicity
in animals and cells in the lab. These 130 studies are significant as a group
because they refer to the exposures as "low dose," implying they are
very relevant to human exposures.

According
to his analysis, however, the "low doses" actually span an immense
range of concentrations, a billion-fold. In addition, only a small fraction of
the exposures in these self-described "low dose" studies are in the
range of human exposures, from 0.8 percent to 7 percent depending on the study.

"The
term low-dose cannot be understood to mean either relevant to human exposures
or in the range of human exposures. However, this is in fact what it has come
to mean to the public, as well as many in the media," said Teeguarden.